Disk Burnable Absorber Reactivity Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing burnable absorbers in nuclear reactors face limitations in design flexibility, manufacturability, and applicability, particularly in achieving very-low-boron or soluble-boron-free operations, which complicates reactivity control and inherent safety in commercial nuclear reactors.

Innovation Solution

A nuclear fuel rod design featuring a cladding tube with alternately stacked fuel pellets and disk-shaped burnable absorbers, utilizing a burnable absorber material like gadolinium (Gd) or erbium (Er) with a zirconium alloy cladding, which exploits the self-shielding phenomenon to adjust reactivity effectively and maintain safety.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If burnable absorber materials are added to adjust excess reactivity, then reactivity control is improved, but device complexity increases due to complicated utility for controlling concentration

Engineering Contradiction:

Improvereactivity controlVSAvoidcomplicated utility

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The burnable absorber material is integrated directly into the fuel pellet structure, merging the reactivity control function with the fuel element itself. This eliminates the need for separate utility systems to control borated water concentration, as the burnable absorber provides inherent reactivity control through its consumption during reactor operation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The burnable absorber material automatically adjusts reactivity as it is consumed during reactor operation. The system is self-regulating, with the absorber material naturally decreasing in concentration as it undergoes transmutation, providing continuous reactivity control without external intervention or complex control utilities.

Inventive Principle:

Principle #25Self-service

2Reliability

If borated water is added to coolant to lower excess reactivity, then reactivity control is improved, but inherent safety deteriorates due to positive moderator temperature coefficient

Engineering Contradiction:

Improvereactivity controlVSAvoidinherent safety

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The burnable absorber material is extracted from the coolant system and integrated into the fuel structure. This removes the harmful effects of borated water on inherent safety while maintaining reactivity control functionality. The fuel assembly itself becomes the reactivity control mechanism, eliminating the need to compromise coolant properties.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The burnable absorber material, which would otherwise be a passive additive requiring complex control, is converted into an active safety feature. As the reactor operates and fuel temperature increases, the burnable absorber continues to provide negative reactivity feedback, enhancing inherent safety rather than compromising it.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If burnable absorber materials are integrated with fuel, then manufacturability is improved, but design flexibility is reduced

Engineering Contradiction:

ImprovemanufacturabilityVSAvoiddesign flexibility

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The burnable absorber material is distributed locally within the fuel pellet structure rather than being uniformly mixed throughout. This localized integration allows different regions of the fuel assembly to have different absorber concentrations, maintaining design flexibility for various reactivity control scenarios while using standard fuel manufacturing processes.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The fuel pellet is designed as a composite structure combining fuel material with burnable absorber material in specific configurations. This composite approach enables tailored reactivity control characteristics while maintaining compatibility with existing fuel manufacturing capabilities, as the composite can be produced using conventional pelletization techniques.

Inventive Principle:

Principle #40Composite materials

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design enhances reactivity control, improves the economic feasibility and safety of nuclear reactors by optimizing the self-shielding effect, allowing for efficient adjustment of excess reactivity and maintaining the integrity of nuclear fuel, even in extreme environments.

Implementation Method 1

The burnable absorber material converts into a material, which has very small neutron absorption probability after absorbing a neutron

Methodology Applied

Scientific EffectNeutron absorption: Absorption (EM radiation)

Implementation Method 2

the burnable absorber is very slowly burnt by using a self-shielding phenomenon

Methodology Applied

Scientific EffectSelf-shielding phenomenon: Shadow

Data Source

PatentEP3817007B1Nuclear fuel rod including disk-type burnable absorber

Publication Date: 2022.07.20 KOREA ADVANCED INST OF SCI & TECH

Figure 1
Figure 2
Figure 3

AI summary

Disclosed is a nuclear fuel rod (10) including at least one or more fuel pellets (11) and a cladding tube (12) surrounding the fuel pellets (11), the nuclear fuel rod (10) including at least one or more burnable absorber (13) inside the cladding tube (12), and the burnable absorber (13) including a burnable absorber material (13a) and a cladding material (13b) surrounding the burnable absorber material (13a).